Conventionally, there has been known an electric parking brake system including an electric motor which operates in response to a driver's switch operation, and a parking brake mechanism which applies a braking force to a wheel as result of operation of the electric motor (see, for example, Patent Document 1). Such an electric parking brake system allows a driver to easily bring the parking brake mechanism into a braking state by merely operating the switch when the vehicle is stopped or parked.
The electric parking brake system of Patent Document 1 performs control of bringing the parking brake mechanism into a braking-released state when it detects that the brake pedal is depressed. Namely, in the case where the parking brake mechanism is in its braking state, when the driver mistakenly operates the switch in a state in which the driver does not depress the brake pedal, the parking brake mechanism is not brought into the braking-released state. Thus, it is possible to prevent occurrence of a situation in which the parking brake mechanism comes into the braking-released state without the driver's awareness.
However, in the case where a device or the like for detecting whether or not the brake pedal is pressed is broken, the driver cannot release the parking brake even when the driver operates the switch while depressing the brake pedal. In such case, the driver must manually release the parking brake mechanism from the braking state, which forces the driver to perform a troublesome operation.
Also, the conventional electric parking brake system cannot meet the demand of releasing the braking of the parking brake mechanism in a state in which the brake pedal is not depressed, if safety is secured, even in the case where the device or the like for detecting whether or not the brake pedal is pressed is not broken.